Comparative assessment of spring soft wheat lines (Triticum aestivum L.) in the steppe zone of the North Kazakhstan region

Spring soft wheat ( Triticum aestivum L.) is one of the most highly demanded crops in Kazakhstan. In 2020, the gross harvest of spring soft wheat reached in recent years the highest outcome of 18.0 million tons. The most important resource for increasing the yield of spring soft wheat is the adaptability and implementation of the variety according to a complex of economically valuable traits. New varieties must be flexible under different environmental conditions. In the presented work, we, for the first time, have identified lines of spring soft wheat well adapted to the conditions of the North Kazakhstan region, distinguished by productivity, a set of economically valuable parameters, environmental stability and plasticity. The aims of the work were i) a comparative assessment of the lines of spring soft wheat of different ripeness groups to the highest extent adapted to the conditions of the steppe zone of Northern Kazakhstan and ii) the assessment of economically valuable traits and their interrelationship with grain yield. The trial was performed using an extended set of spring soft wheat lines of various ripeness from research centers of Kazakhstan (fallow soil, the North Kazakhstan Agricultural Experimental Station LLP, Republic of Kazakhstan, 2018-2020). A total of 28 lines were studied, including 20 middle-early and 8 mid-season lines. Two cultivars registered in North Kazakhstan region served as the standards, the middle-early cv. Astana and the mid-season cv. Omskaya 35. The duration of inter phase and vegetation periods, yield and the main elements of yield structure were studied. The length of growing season was 79 days for the mid-early lines and 80 days for the mid-ripening lines. A shorter growing season was characteristic for the mid-early lines Lutescens 1125 SP 2/09 (73 days), Lutescens 528 (74 days), Lutescens 630 SP 2/08 (74 days), Lutescens 742 SP 2/19 (74 days), Lutescens 715 SP 2/04 (75 days), Lutescens 687 SP 2/04(75 days), Lutescens 1148 SP 2/09 (76 days) vs. the standard cv. Astana (79 days). In the mid-season group, the Liniya 12/93-01(82 days), Liniya 33/93-01-15 (82 days), Lutescens 2194 (82 days), Lutescens 1919 (85 days) stood out for the optimal length of growing season vs. the standard cv. Omskaya 35 (80 days). In terms of crop yield in the mid-early ripeness group, the following lines were distinguished: Lutescens 588 SP 2/05 (2.3 t/ha), Erythrospermum 738 2/09 (2.3 t/ha), Lutescens 857 SP 2/05 (2.4 t/ha), Lutescens 821 SP 1/08 (2.4 t/ha), Lutescens 715 SP 2/04 (2.4 t/ha) vs. cv. Astana (2.0 t/ha). In the mid-season group, Lutescens 371/06 (2.4 t/ha), Line 12/93-01-10 (2.4 t/ha), Lutescens 1919 (2.5 t/ha), Line 55/94-01 (2.6 t/ha), and Line 33/93-01-15 (2.8 t/ha) were superior to cv. Omskaya 35 (1.8 t/ha). In the studied mid-early lines, the main elements of the yield structure were the number of productive stems (154-244 stems/m2), the grain number per ear (21-28 grains), and the 1000-grain weight of 36.6-43.4 g. In the mid-season group, the number of productive stems was 170-252 stems/m2, the number of grains per ear was 23-30 grains, and the 1000-grain weight of was 34.2-45.2 g. The yield of mid-early lines showed correlation with the grain number per ear ( r = 0.35-0.86, p = 0.36-1.29) and tight correlation with the number of productive stems ( r = 0.68-0.83, p = 0.82-1.18). The yield of mid-season lines correlated with the number of productive stems ( r = 0.74-0.86, p = 0.95-1.29) and the grain number per ear ( r = 0.31-0.71, p = 0.32-0.88). The correlation between yield of the studied lines and the 1000-grain weight was medium ( r = 0.37-0.54, p = 0.38-0.60) and, in a dry year, weakly negative ( r = -0.16, p = 0, 16). Therefore, for the North Kazakhstan steppe zone, we propose to involve the mid-early lines Lutescens 715 SP2/04, Lutescens 821 SP2/08, Lutescens 588 SP2/05, Erythrospermum 738 2/09 and mid-season Line 33/93-01-15, Line 55/94-01, Lutescens 371/06, Lutescens 1919, Line 12/93-01-10 in breeding for drought resistance and adaptive potential.